#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time    : 2020/10/24 11:19
# @USER    : Shengji He
# @File    : VideoStitching.py
# @Software: PyCharm
# @Version  : Python-
# @TASK:
from typing import List


class Solution:
    def videoStitching(self, clips: List[List[int]], T: int) -> int:
        """
        You are given a series of video clips from a sporting event that lasted T seconds. These video clips can be
        overlapping with each other and have varied lengths.

        Each video clip clips[i] is an interval: it starts at time clips[i][0] and ends at time clips[i][1].
        We can cut these clips into segments freely: for example, a clip [0, 7] can be cut into
        segments [0, 1] + [1, 3] + [3, 7].

        Return the minimum number of clips needed so that we can cut the clips into segments that cover the entire
        sporting event ([0, T]).  If the task is impossible, return -1.

        Example 1:
            Input: clips = [[0,2],[4,6],[8,10],[1,9],[1,5],[5,9]], T = 10
            Output: 3
            Explanation:
                We take the clips [0,2], [8,10], [1,9]; a total of 3 clips.
                Then, we can reconstruct the sporting event as follows:
                We cut [1,9] into segments [1,2] + [2,8] + [8,9].
                Now we have segments [0,2] + [2,8] + [8,10] which cover the sporting event [0, 10].
        Example 2:
            Input: clips = [[0,1],[1,2]], T = 5
            Output: -1
            Explanation:
                We can't cover [0,5] with only [0,1] and [1,2].
        Example 3:
            Input: clips = [[0,1],[6,8],[0,2],[5,6],[0,4],[0,3],[6,7],[1,3],[4,7],[1,4],[2,5],[2,6],[3,4],[4,5],[5,7],
            [6,9]], T = 9
            Output: 3
            Explanation:
                We can take clips [0,4], [4,7], and [6,9].
        Example 4:
            Input: clips = [[0,4],[2,8]], T = 5
            Output: 2
            Explanation:
                Notice you can have extra video after the event ends.

        Constraints:
            - 1 <= clips.length <= 100
            - 0 <= clips[i][0] <= clips[i][1] <= 100
            - 0 <= T <= 100
    
        :param clips:
        :param T:
        :return:
        """
        maxn = [0] * T
        last = ret = pre = 0
        for a, b in clips:
            if a < T:
                maxn[a] = max(maxn[a], b)
        for i in range(T):
            last = max(last, maxn[i])
            if i == last:
                return -1
            if i == pre:
                ret += 1
                pre = last

        return ret


if __name__ == '__main__':
    print('done')
